1. Field of the Invention
The present invention relates to a fuel injection valve for an internal combustion engine, and more particularly to a fuel injection valve suitable for use in a direct-injection internal combustion engine, which injects fuel directly into a cylinder.
2. Background Art
A fuel injection valve for opening/closing a flow path by operating a needle valve is disclosed, for instance, by Japanese Patent Laid-Open No. 147317/2002. This fuel injection valve is such that the diameter of a flow path positioned downstream of a seat section with which the needle valve comes into contact is increased by tapering. Deposits in the flow path positioned downstream of a seat section decrease the cross-sectional area of the flow path, thereby reducing the fuel injection amount. The above conventional fuel injection valve is configured as described above to increase the amount of fuel flow on the downstream side of the seat section, thereby enhancing the effect of removing carbon deposits in the flow path positioned downstream of the seat section.
In fuel injection valves for an internal combustion engine, the amount of deposits increases when the capacity of the flow path positioned downstream of the seat section increases to increase the amount of fuel remaining in the flow path. According to a method employed by the above conventional fuel injection valve, the flow of fuel on the downstream side of the seat section can be improved; however, it is difficult to effectively avoid the accumulation of deposits. The reason is that the capacity of the flow path on the downstream side of the seat section is increased. Further, if the capacity of the flow path on the downstream side of the seat section is increased naively as in the case of the above conventional fuel injection valve, the spray characteristic might be impaired.